Disclosed herein is a dual parallel Mach-Zehnder-modulator (DPMZM) device comprising a DPMZM 10 having first and second inner MZMs arranged parallel to each other. The first inner MZM generates an in-phase component E.sub.I of an optical signal in response to a first driving voltage V.sub.I, and the second inner MZM generates a quadrature component E.sub.Q of said optical signal in response to a second driving voltage V.sub.Q. Further disclosed is a calculation unit 52 configured for receiving an in-phase component y.sub.I and a quadrature component y.sub.Q of a desired base-band signal, and for calculating pre-distorted first and second driving voltages V.sub.I, V.sub.Q. The calculation of the pre-distorted first and second driving voltages V.sub.I, V.sub.Q is based on a model of said DPMZM 10 accounting for I-Q cross-talk, and using an algorithm that determines said first and second driving voltages V.sub.I, V.sub.Q each as a function of both of said in-phase and quadrature components y.sub.I, y.sub.Q of said base-band signal.

An optical frequency manipulation using an optical subsystem configured to provide a modulated laser beam for interaction with an atomic sample. The optical system may include: an optical subsystem for producing a light beam, the optical subsystem having a laser source and an IQ modulator, wherein the IQ modulator is operable to modulate light from the laser source at a carrier frequency to produce modulated light having a single sideband at a sideband frequency; and a chamber for containing an atomic sample, wherein the optical subsystem is arranged to direct the light beam towards the chamber to interact with an atomic sample contained therein.

A Mach-Zehnder modulator is enabled to perform high-speed modulation operation by reducing RF loss of a high-frequency wiring formed on an optical waveguide without deteriorating optical characteristics of branching and multiplexing optical circuits. The Mach-Zehnder modulator includes a Mach-Zehnder (MZ) optical waveguide including two arm waveguides, a 1×2 multimode interference coupler composed of a semiconductor that splits and distributes input light to the two arm waveguides, a 2×1 multimode interference coupler composed of a semiconductor that multiplexes light from the two arm waveguides, and phase modulation means for giving a phase difference to the light that propagates through the two arm waveguides, wherein the 1×2 multimode interference coupler and the 2×1 multimode interference coupler are formed in a high-mesa structure, and higher mode light radiation means for radiating higher mode light is connected to only the 2×1 multimode interference coupler among the two multimode interference couplers.

A semiconductor optical modulator includes a modulation region and a non-modulation region. A first width of a first ground electrode in the non-modulation region is larger than a second width of the first ground electrode in the modulation region. A third width of a second ground electrode in the non-modulation region is larger than a fourth width of the second ground electrode in the modulation region. In the non-modulation region, a first insulating layer is disposed between a first optical waveguide and a first traveling wave electrode and between a second optical waveguide and a second traveling wave electrode. For this reason, a bandwidth of the semiconductor optical modulator can be widened.

In an embodiment, a method and apparatus for increasing bandwidth of an optical modulator by applying a first voltage applied to a beginning of a resistive line and applying a second voltage applied to an end of the resistive line; wherein the first voltage is less than the second voltage.

A silicon-based optical modulator. An optical modulator of a Mach-Zehnder type includes an optical coupler configured to separate a single optical signal into two optical signals having same output power, two phase shifters having a PN junction through which the two optical signals separated through the optical coupler pass respectively, a plurality of electrodes configured to apply an electrical signal to the two phase shifters, and two PN diodes disposed between the two phase shifters and configured to adjust an operating bandwidth of the optical modulator. The optical signals respectively passing through the two phase shifters have phases that change as a width of a depletion region changes based on a magnitude of a reverse voltage provided to the two phase shifters through the electrodes and a refractive index changes.

A Mach Zehnder modulator operates by phase modulating split optical beams with a modulating signal to create dissimilarities in the optical characteristics between the split beams. When the beams are recombined, the dissimilarities gives rise to intensity modulations that are indicative of the modulating signal. One or both beams are modulated with an RF trimming signal. The trimming signal is applied asymmetrically across the two beams thereby reducing the intensity of the optical carrier frequency in one of the beams more than in the other. By selecting the size of the trimming signal the differences in the optical amplitude of the carrier frequency in the two beams can be nulled.

Phase modulation electrode lines of a semiconductor Mach-Zehnder optical modulator are formed along waveguides. Output-side lead lines are bent in a direction crossing the extending direction of the waveguides in the plane of a dielectric layer and are connected to terminal resistors. The output-side lead lines are formed in a predetermined width corresponding to a desired impedance and make the width narrower than the predetermined width only in the bent portions and portions where the output-side lead lines crosses the waveguides.

An optical modulator includes a first mesa waveguide and a second mesa waveguide. Each of the first mesa waveguide and the second mesa waveguide includes a first semiconductor layer that has a p-type conductivity and is provided on a substrate, a second semiconductor layer that has a p-type conductivity and is provided on the first semiconductor layer, a core layer provided on the second semiconductor layer, and a third semiconductor layer that has an n-type conductivity and is provided on the core layer. The first semiconductor layer has a dopant concentration greater than a dopant concentration in the second semiconductor layer.

An optical modulator, that includes a Mach-Zehnder interferometer and three or more segments, generates an optical signal based on three or more electric signals transmitted in parallel. The three or more segments are provided in series along an optical path of the Mach-Zehnder interferometer and respectively shift a phase of light propagating through the optical path based on the three or more electric signals. A length of at least one of the three or more segments is different from lengths of the other segments. Optical path lengths from input ends of respective segments to input ends of corresponding next segments are the sae.